Hackingly instruct jest not to transform any files
Hackingly instruct jest not to transform any files

Before it detected .babelrc and used it to transpile all files,
even though it works fine with the untranspiled files.

This causes arrow functions to come out as old-style functions,
which affects their .toString(), causing breakage like:
https://travis-ci.org/unexpectedjs/unexpected/jobs/434942547

Prerequisite for #522

unexpectedjs/unexpected